【Hive】HiveQL：数据操作

本篇主要演示Hive的数据操作，包括向表中装载数据、插入数据、创建表以及导出数据。

一 向表中装载数据

1 语法结构

LOAD DATA [LOCAL] INPATH 'filepath' [OVERWRITE] INTO TABLE tablename [PARTITION (partcol1=val1, partcol2=val2 ...)]

2 示例

hive> load data local inpath '/home/hadoop/emp/'
    > into table emp;
Loading data to table hive.emp
OK
Time taken: 0.95 seconds
hive> select *from emp;
OK
emp.id	emp.name
1	Alen
2	Jane
3	Tom
4	Peter
Time taken: 0.252 seconds, Fetched: 4 row(s)
hive> 

二 通过查询语句向表中插入数据

1 语法结构

INSERT OVERWRITE TABLE tablename1 [PARTITION (partcol1=val1, partcol2=val2 ...) [IF NOT EXISTS]] select_statement1 FROM from_statement;
INSERT INTO TABLE tablename1 [PARTITION (partcol1=val1, partcol2=val2 ...)] select_statement1 FROM from_statement;
 
Hive extension (multiple inserts):
FROM from_statement
INSERT OVERWRITE TABLE tablename1 [PARTITION (partcol1=val1, partcol2=val2 ...) [IF NOT EXISTS]] select_statement1
[INSERT OVERWRITE TABLE tablename2 [PARTITION ... [IF NOT EXISTS]] select_statement2]
[INSERT INTO TABLE tablename2 [PARTITION ...] select_statement2] ...;
FROM from_statement
INSERT INTO TABLE tablename1 [PARTITION (partcol1=val1, partcol2=val2 ...)] select_statement1
[INSERT INTO TABLE tablename2 [PARTITION ...] select_statement2]
[INSERT OVERWRITE TABLE tablename2 [PARTITION ... [IF NOT EXISTS]] select_statement2] ...;
 
Hive extension (dynamic partition inserts):
INSERT OVERWRITE TABLE tablename PARTITION (partcol1[=val1], partcol2[=val2] ...) select_statement FROM from_statement;
INSERT INTO TABLE tablename PARTITION (partcol1[=val1], partcol2[=val2] ...) select_statement FROM from_statement;

2 示例

hive> create table t_emp(id int , name string);
OK
Time taken: 1.611 seconds
hive> insert overwrite table t_emp
    > select *from emp;
hive> select *from t_emp;
OK
t_emp.id	t_emp.name
1	Alen
2	Jane
3	Tom
4	Peter
Time taken: 0.296 seconds, Fetched: 4 row(s)

三 单个查询语句中创建表并加载数据

通过Create Table AS实现：

hive> create table t_emp as
    > select *from emp;
hive> select *from t_emp;
OK
t_emp.id	t_emp.name
1	Alen
2	Jane
3	Tom
4	Peter
Time taken: 0.311 seconds, Fetched: 4 row(s)

四 导出数据

1 语法结构

Standard syntax:
INSERT OVERWRITE [LOCAL] DIRECTORY directory1
  [ROW FORMAT row_format] [STORED AS file_format] (Note: Only available starting with Hive 0.11.0)
  SELECT ... FROM ...
 
Hive extension (multiple inserts):
FROM from_statement
INSERT OVERWRITE [LOCAL] DIRECTORY directory1 select_statement1
[INSERT OVERWRITE [LOCAL] DIRECTORY directory2 select_statement2] ...
 
  
row_format
  : DELIMITED [FIELDS TERMINATED BY char [ESCAPED BY char]] [COLLECTION ITEMS TERMINATED BY char]
        [MAP KEYS TERMINATED BY char] [LINES TERMINATED BY char]
        [NULL DEFINED AS char] (Note: Only available starting with Hive 0.13)

2 示例

hive> insert overwrite local directory  '/home/hadoop/emp'
    > select *from emp;
[hadoop@strong ~]$ vim /home/hadoop/emp/000000_0 
1^AAlen
2^AJane
3^ATom
4^APeter

注：数据中的列与列之间的分隔符是^A(ascii码是0001)。

3 使用Hadoop命令导出

[hadoop@strong ~]$ hadoop fs -copyToLocal /user/hive/warehouse/hive.db/emp/ /home/hadoop/
[hadoop@strong ~]$ cat emp/*
1Alen
2Jane
3Tom
4Peter

五 插入值到表中

1 语法结构

Standard Syntax:
INSERT INTO TABLE tablename [PARTITION (partcol1[=val1], partcol2[=val2] ...)] VALUES values_row [, values_row ...]
  
Where values_row is:
( value [, value ...] )
where a value is either null or any valid SQL literal

2 示例

hive> insert into emp values(5,'Jack'),(6,'Winter');

六 修改操作

1 语法结构

Standard Syntax:
UPDATE tablename SET column = value [, column = value ...] [WHERE expression]

注：update操作仅仅在支持ACID的表上执行。

七 删除操作

1 语法结构

Standard Syntax:
DELETE FROM tablename [WHERE expression]

注：delete操作仅仅在支持ACID的表上执行。

八 合并操作

1 语法结构

Standard Syntax:
MERGE INTO <target table> AS T USING <source expression/table> AS S
ON <boolean expression1>
WHEN MATCHED [AND <boolean expression2>] THEN UPDATE SET <set clause list>
WHEN MATCHED [AND <boolean expression3>] THEN DELETE
WHEN NOT MATCHED [AND <boolean expression4>] THEN INSERT VALUES<value list>

注：merge操作仅仅在支持ACID的表上执行。

更多内容可参考：https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DML